This invention pertains to a gas-fired fryer of a type used in restaurants and elsewhere to fry fish, poultry, potatoes, and foods of other kinds in a frypot containing a frying oil. This invention also pertains to a gas-fired burner, in which gas to be burned is injected into a vortex of air, of a type useful for a gas-fired fryer.
As exemplified in U.S. Pat. Nos. 2,429,360, 2,452,472, 2,655,144, and 2,712,308, one type of gas-fired fryer employs tubular heaters, which are mounted within the frypot, so as to be immersed in the frying oil. Heat is transferred efficiently from the heaters to the frying oil in the frypot. However, such heaters tend to become fouled with burnt-on residues and to be difficult to clean. Typically, such heaters comprise several tubular elements, which are crowded in lower portions of the frypot. Typically, such a fryer has a lower zone, in which particles of food and breading tend to collect, which is unheated, so as to avoid scorching of particles collected therein, and which tends to be difficult to clean when spanned by such tubular elements.
Gas-fired fryers of related interest are examplified in U.S. Pat. Nos. 2,251,111, 3,313,288, 3,970,072, 3,990,433, and 4,228,730. Gas-fired devices of related interest but for other uses are exemplified in U.S. Pat. Nos. 2,185,594, 2,465,953, 3,554,182, and 4,014,316.
Also, another type of gas-fired fryer employs gas-fired heaters mounted beneath but outside the frypot, so as to facilitate cleaning of the frypot, which thus can be free of internal tubular structures tending to become fouled with burnt-on residues and to be difficult to clean. However, particles of food and breading tend to collect on and to be burnt onto heated lower portions of the frypot.
U.S. Pat. No. 4,091,801 discloses such a fryer, in which heat is transferred to the frying oil in the frypot via a vaporized fluid. U.S. Pat. No. 3,964,378 disclosed another type of gas-fired device of related interest.
As exemplified in U.S. Pat. Nos. 3,809,062, 3,938,948, and 3,948,593, another type of gas-fired fryer employs gas-fired burners adjacent to lateral walls of a lower portion of the frypot. Heat is transferred efficiently from the burners to the frying oil in the frypot through such walls, which are oriented vertically where adjacent to the burners, so as to minimize horizontal surfaces tending to allow boundary layers of hot frying oil to form along such surfaces.
Gas-fired burners of the type mentioned above are exemplified in numerous references including U.S. Pat. Nos. 2,539,165, 2,565,879, 2,787,318, 3,630,651, 4,124,353, and 4,224,019.
Against a background of increased costs of gaseous fuels in recent years, gas-fired fryers employing gas-fired burners of high efficiency are expected to displace less efficient fryers in restaurants and elsewhere.
Additionally, it is known for flow of gas to a main burner to be delayed by suitable means for a minimum delay after combustion has been established at a pilot burner, in a furnace wherein air is drawn into the burner by a partial vacuum created in the furnace, and wherein air and gas to be burned are mixed at each such burner. However, such means do not seem to have been used heretofore in a burner wherein air and gas to be burned are mixed in a vortex of air, and wherein the vortex of air is provided from air delivered to the burner at low pressure, which may be as low as 1.5 inches of water.